Intrastromal refractive correction systems and methods

ABSTRACT

Devices, systems, and methods for laser eye surgery selectively ablate tissues within the cornea of an eye along one or more target surfaces, so that corneal tissue bordered by the laser incision surface(s) can be mechanically removed. An appropriate tissue-shaping surface can be selected based on the regular refractive error of the eye, and a shape of the target laser surface(s) can be calculated so as to correct irregular refractive errors of the eye, impose desired additional sphero-cylindrical and/or irregular alterations.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a nonprovisional application claims the benefit ofU.S. provisional patent application No. 60/783,306, filed on Mar. 17,2006, the disclosure of which is incorporated herein by reference.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH OR DEVELOPMENT

NOT APPLICABLE

REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISK

NOT APPLICABLE

BACKGROUND OF THE INVENTION

This invention generally relates to laser eye surgery devices, systems,and methods. In particular embodiments, the invention providestechniques for selectively altering refractive properties of corneashaving regular and/or irregular optical defects, often by directingenergy into the stroma.

Laser eye surgery systems and methods are now used to correct defects invision, often using a technique known as ablative photodecomposition. Ingeneral, this technique applies a pattern of laser radiation to anexposed corneal tissue so as to selectively remove and resculpt thecornea. The pattern of laser energy often includes a series of discretelaser pulses from an excimer laser, with the locations, sizes, and/ornumbers of pulses of the pattern being calculated to achieve a desiredvolumetric resculpting of the cornea, and to thereby create enhancedoptical properties or treat optical defects.

Many patients suffer from optical defects which are not easily treatedusing standard glasses and contact lenses. Glasses and contacts oftentreat only regular or spherical and cylindrical refractive errors of theeye. Wavefront diagnostic techniques have been developed to measureirregular refractive errors, and these techniques have proven highlyuseful in determining customized refractive prescriptions for thesepatients. The flexibility of laser photorefractive decomposition offershope to these patients, as this technique can be used to resculpt theeyes to correct both regular and irregular refractive errors. Bycombining laser eye surgery techniques with wavefront diagnosticapproaches, it is often possible to achieve visual acuity measurementsof 20/20 or better for many patients.

Early laser eye surgery treatments often involved the removal of theepithelial layer before changing the shape of the underlying cornealtissue. The epithelial layer tends to regrow, whereas volumetricresculpting of the underlying stroma can provide long-lasting effects.Corneal resculpting techniques involving mechanical abrasion or laserablation of the epithelial layer so as to expose the underlying stromafor volumetric photoablative decomposition are often referred to asphotorefractive keratectomy (“PRK”), and PRK remains a good option formany patients. In the last several years, alternative techniquesinvolving formation of a flap of corneal tissue (including theepithelial layer) have gained in popularity. Such techniques aresometimes popularly referred to “flap-and-zap,” or laser in situkeratomileusis (“LASIK”). LASIK and related variations often have theadvantage that vision can be improved within a few hours (or evenminutes) after surgery is complete. LASIK flaps are often formed usingmechanical cutting blades or microkeratomes, and the flap of epithelialtissue can be temporarily displaced during laser ablation of the stroma.The flap can reattach to the underlying stroma quite quickly, and thepatient need not wait for epithelial tissue regrowth to experience thebenefits of laser resculpting, so that these procedures are safe andhighly effective for many patients.

A variety of alternative refraction altering techniques have also beenproposed. In particular, focusing of femtosecond laser energy within thestroma so as to ablate a volume of intrastromal tissue has beenproposed. By scanning the focal spot within an appropriate volume of thestromal tissue, it might be possible to vaporize the volume so as toachieve a desired refractive alteration. Despite possible advantages ofintrastromal volumetric ablation techniques, these approaches have notyet gained the popularity of LASIK and/or PRK. Intrastromal femtosecondablation techniques have, however, begun to gain popularity as a methodfor incising the cornea so as to form the flap of corneal tissue inLASIK and related procedures. Unfortunately, this combined approachoften involves the use of both a fairly expensive intrastromalfemtosecond laser for incising the corneal tissues, and then an excimerlaser for resculpting the exposed stroma. The combined use these twoseparate, fairly complex and/or expensive laser systems may limit theacceptability and benefits of these new refractive laser eye surgerytechniques.

In light of the above, it would generally be desirable to provideimproved devices, system, and methods for laser eye surgery. It would beparticularly desirable to expand the capabilities of lasers and allowtheir use for both incising and refractively altering the eye. It wouldbe particularly desirable if such improved devices were suitable forcorrection of regular refractive errors and a irregular refractivealterations (such as correcting an irregular refractive error of theeye), ideally without having to resort to two separate laser systems.

BRIEF SUMMARY OF THE INVENTION

The present invention generally provides improved devices, systems, andmethods for laser eye surgery. In many embodiments, the invention willmake use of femtosecond (or optionally picosecond) lasers and theirability to selectively ablate tissues within the cornea of an eye. Byfocusing energy from these lasers at a focal spot within a cornealstroma, and by scanning the spot along a surface, such lasers canquickly and accurately incise the corneal tissues along that surface.Rather than attempting to rely on volumetric intrastromal tissuevaporization, embodiments of the invention may largely (or evenprimarily) employ mechanical removal of tissues bordered by a laserincision surface. Advantageously, large variations in depth of the focalspot from a plane (or other surface, such as a sphere or the like) maybe avoided by pre-shaping the corneal tissues using a tissue-shapingsurface. By selecting an appropriate tissue-shaping surface based on theregular refractive error of the eye, and by calculating an appropriatetissue incision surface so as to correct irregular refractive errors ofthe eye, the corneal reshaping may mitigate both regular and irregularrefractive defects, with the laser treatment typically being completedin less than 100 seconds, often being completed in less than 50 seconds,in many cases being completed in less than 30 seconds, and in some casesbeing completed in less than 10 seconds between initiation of andcompletion of the laser ablation.

In a first aspect, the invention provides a method for alteringrefraction of an eye. The eye has a regular refractive error and iscapable of benefiting from a desired irregular refractive alteration.The method comprises selecting a tissue-shaping surface substantiallycorresponding to the regular refractive error. The selected tissueshaping surface is engaged against the eye so as to conform the eye tothe selected tissue-shaping surface. A laser target surface isdetermined in response to the desired irregular refractive alteration ofthe eye. A laser spot is scanned through the tissue of the eye along thelaser target surface so as to mitigate the regular error and effect thedesired irregular refractive alteration of the eye.

In many embodiments, the desired irregular refractive alteration of theeye will comprise correction of irregular refractive defects, typicallybased on wavefront measurements of the eye. Other desirable irregularrefractive alterations may include imposing a presbyopia-mitigatingrefractive shape on the eye. Such irregular refractive alterations willoften be customized for a particular patient, optionally being based onpupil measurements taken from the eye under different viewing conditionsand the like.

An appropriate tissue-shaping surface will often be selected by choosinga shaping body from among a set of alternative shaping bodies. Theshaping bodies will each have tissue-shaping surfaces that correspond toan associated regular refractive error. For example, one subset of thebodies may be used for patients having about 2.0 D of myopia, withmembers of this subset each having an associated astigmatism power (forexample, −2.0 D, 0 D, +2 D, 4 D . . . of cylinder). Another subset ofthe bodies may have surface with 4 D of myopia (and differing amounts ofastigmatism), and so on. The steps in spherical and cylindrical powerbetween the various shaping bodies of the set may be uniform (such ashaving steps of 0.5 D, steps of 1.0 D, steps of 1.5 D, or the like) orthe incremental step size may vary throughout the set. Regardless, theactual regular error of the eye will often differ at least slightly fromthe power of the selected shaping body. Advantageously, the laser targetsurface may be calculated so as to compensate for this power difference.Hence, when a patient has 2.3 D of myopia, and the substantiallycorresponding tissue-shaping surface has 2.0 D of spherical power, thelaser target surface may be adjusted so as to provide an additional 0.3D of spherical power to fully correct the patient's myopia. Typically,the steps in power between the tissue-shaping surfaces of the set willeach be less than or equal to two times a maximum power adjustmentavailable from the laser target surface. In exemplary embodiments, thesteps in power may be less than or equal to 3.0 D, often being less thanor equal to 1.5 D, and in some embodiments being less than or equal 0.75D.

In exemplary embodiments, each of the set of shaping bodies maycomprises a material transmissive of the laser energy used to form thespot. Each shaping body may have alignment surfaces for aligning bodyboth along an optical path of the laser energy and rotationally aboutthe optical path. The bodies may each also have a signal sourceconfigured to generate a signal indicative of an associated power ofthat body, and of an identifier of that particular body. This may allowthe signals to be used for verifying that an appropriate body has beenmounted to the laser eye surgery system, and for inhibiting reuse ofeach of the alternative selectable bodies. Suitable signal sources maycomprise a memory chip, a radio frequency identification (“RFID”) tag,or the like.

In many cases, the regular error of the eye will comprise a cylindricalerror having an astigmatism axis. The tissue-shaping surface will oftenbe rotated into alignment with the astigmatism axis of the eye.Alignment between the tissue-shaping surface and the eye may be checkedafter engaging the tissue-shaping surface against the eye, such as bycapturing an image of the eye through the tissue shaping surface so asto determine horizontal and/or cyclotorsional offsets between theengaged eye and the tissue-shaping surface. Optionally, thetissue-shaping surface may be displaced away from the eye, and eitherthe eye or the tissue-shaping surface moved so as to correct alignmentbefore again engaging the tissue-shaping surface against the eye. Whilesuch repositioning may be appropriate when the offsets exceed athreshold, some limited alignment offsets may be acceptable. The rangeof acceptable offsets may be increased by adjusting a location and/or ashape of the target laser surface in response to any alignment offsets.

In many embodiments, tissue will be at least partially mechanicallyexcised from between the target laser surface and the tissue-shapingsurface. By removing substantially all of the tissue between the targettissue surface and the tissue-shaping surface (often after separation ofthe tissue-shaping surface from the eye) both regular and irregularrefractive errors of the eye can be corrected, with the benefits of thecorrection often being provided after epithelial regrowth. In otherembodiments, the laser spot may be scanned along another laser targetsurface so that first and second tissue surfaces are defined by the twolaser target surfaces. Tissue may be mechanically excised from betweenthese two laser-formed tissue surfaces so that the eye has enhancedrefractive characteristics when the two tissue surfaces engage eachother, and without having to wait for epithelial regrowth.

In another aspect, the invention provides a method for customizedcorrection of an eye. The method comprises measuring a regularrefractive error and an irregular refractive error of the eye. Theregular refractive error comprises a spherical error and a cylindricalerror. The cylindrical error has a cylindrical power and an astigmatismaxis. A tissue-shaping body is selected in response to the regularrefractive error of the eye. The tissue-shaping body is selected fromamong a set of alternative tissue-shaping bodies having differingassociated spherical and cylindrical powers. The selected tissue-shapingbody has a selected tissue-shaping surface with a spherical powersubstantially corresponding to the spherical power of the eye and acylindrical power substantially corresponding to the cylindrical errorof the eye. A cylindrical axis of the selected tissue-shaping body isaligned with the astigmatism axis of the eye, and the selectedtissue-shaping surface is engaged against the eye so as to conform aneye surface to the selected tissue-shaping surface. A target lasersurface is determined in response to the irregular refractive error ofthe eye, and tissue of the eye is incised by scanning a laser spotthrough the tissue along the laser target surface. Tissue bordered bythe laser target surface is mechanically excised so as to mitigate theregular refractive error and the irregular refractive error of the eye.

In many embodiments, the target laser surface differs from a nominalsurface shape (such as a plane or a sphere) by less than a depththreshold, the depth threshold corresponding to a power of about 1.5diopters or less.

In another aspect, the invention provides a system for alteringrefraction of an eye. The eye has a regular refractive error and iscapable of benefiting from an irregular refractive alteration. Thesystem comprises a set of alternative tissue-shaping bodies havingtissue-shaping surfaces and differing regular refractive powers. Atissue incising laser transmits a laser beam along an optical path, anda support positions a selected tissue-shaping body along the opticalpath. The selected tissue-shaping body is selected from among the set. Aprocessor determines a laser target surface in response to the desiredirregular refractive alteration of the eye. Beam scanning optics scanthe beam along the laser target surface to incise tissue of the eye whenthe eye engages and conforms to the selected tissue-shaping surface suchthat removal of the incised tissue mitigates the regular error of theeye and effects the desired irregular alteration.

In another aspect, the invention provides a tissue-shaping body for usewith a system to alter refraction of an eye. The eye will often have aregular refractive error and an irregular refractive error, the systemincluding a support for positioning the shaping body along an opticalpath from a laser and beam scanning optics for scanning along a targetsurface to incise tissue of the eye when the eye engages the body suchthat removal along the incised tissue surface mitigates the regular andirregular errors of the eye. The body comprises a material transmissiveof light from the laser, and a tissue shaping surface defined by thematerial. The tissue-shaping surface has a cylindrical powersubstantially corresponding to the regular refractive error of the eye.

In many embodiments, the body will also include a signal source fortransmitting a signal. The signal will typically be indicative of thecylindrical power, and of an identifier of the particular body, theidentifier typically comprising a serial number, an inventory number, orthe like suitable for inhibiting reuse of that body. The body may beincluded in a set of alternatively selectable tissue-shaping bodieshaving differing tissue-shaping surfaces corresponding to differingcylindrical and spherical refractive powers. Each body will often havemounting interface surfaces for mounting the body relative to the lasersystem, with the mating interface surfaces generally positioning thetissue-shaping surface axially along an optical path of the laser androtationally about the optical path so as to facilitate alignment of thecylindrical power of the body with an astigmatism axis of the eye. Thebody may also have (or be associated with) indicia of alignment tofacilitate aligning the tissue-shaping surface and eye, for measuringhorizontal and rotational offsets between the tissue-shaping surface andthe eye, and/or he like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an exemplary laser eye surgery systemand method of its use for correcting regular and irregular refractiveerrors of an eye.

FIG. 1A is a schematic perspective view of a laser-eye surgery systemand patient support system, components of which may be modified for usein the system of FIG. 1.

FIG. 2 is a schematic illustration of a data processing computer systemfor use in the laser eye surgery systems of FIGS. 1 and 1A.

FIG. 3 schematically illustrates a wavefront measurement system formeasuring the regular and/or irregular refractive errors of the eye foruse with the surgical systems of FIGS. 1 and 1A.

FIG. 4 is a schematic side view of a simplified model of an eye andtissue-shaping surface and body for use in the system of FIG. 1.

FIG. 5 is a schematic illustration of an image taken from along theoptical path through the image shaping body of FIG. 4, showinghorizontal and rotational alignment offsets between the tissue shapingbody and tissues of the eye, as maybe identified using image processingsoftware in the system of FIG. 1.

FIG. 6 is a schematic side view showing engagement between thetissue-shaping surface and cornea, and also shows a tissue incisiondepth range.

FIG. 7 is a detailed side view of the tissue-engaging surface andcorneal tissue conforming thereto from FIG. 6, and shows laser incisionof the corneal tissue along a target tissue surface within a limiteddepth range, such that both the regular and irregular refractive errorsof the eye ere mitigated.

FIG. 7A is a schematic side illustration of the tissue-shaping surfaceand corneal tissue after the incision of the FIG. 7 is complete, andafter the tissue between the target tissue surface and tissue-shapingbody has been removed.

FIG. 8 schematically illustrates an alternative system and method inwhich two tissue surfaces are incised by the laser.

FIGS. 8A and 8B schematically illustrates displacement of an epithelialflap, removal of tissue between the target tissue surfaces, andreplacement of the flap with effective refractive correction for bothregular and irregular refractive errors.

FIG. 8C illustrates embodiments of methods and systems related to thoseof FIG. 8A, with the irregular refractive error being compensated forusing the anterior laser target surface and the posterior laser targetsurface being planer.

FIG. 8D illustrates an alternative tissue-shaping body having aplurality of tissue-shaping surfaces.

FIG. 9 schematically illustrates some of the optical and structuralcomponents of the laser system of FIG. 1.

FIGS. 10A and 10B are top and side views, respectively, of a laserdelivery arm of the system of FIG. 1.

FIG. 11 is a flow chart schematically illustrating a method for treatingan eye so as to correct regular and irregular refractive errors.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The present invention generally provides improved devices, systems, andmethods for refractive correction of an eye. Embodiments of theinvention can take advantage of the capabilities of femtosecond lasers,picosecond lasers and the like, to incise the eye along preciselydefined target surfaces. Advantageously, the volume of each individuallaser ablation need not be precisely known and/or controlled,particularly when the total volume of tissue removal will be muchgreater than the overall volumetric ablation. Even when the absolutedepth of individual ablations is not perfectly controlled or known,focused intrastromal laser ablations may be able to incise the cornealtissue along a surface shape with sufficient accuracy (such as bycontrolling the depths of ablation spots along a target surface relativeto each other) so as to provide a desired high order resculpting of theoverall cornea. By relying at least in part on incising and mechanicalremoval of tissues along the incised tissue surfaces (rather than solelyor even primarily on volumetric photoablation), precise corrections maybe provided very rapidly.

Many embodiments of the invention will make use of a selected cornealtissue-shaping surface, with the surface often being selected inresponse to a low-order, regular refractive error of the eye. Bypre-shaping the tissue of the eye using a tissue-shaping surface thatsubstantially corresponds to the regular refractive error of the eye,and by calculating a three-dimensional laser target surface based onirregular refractive errors of the eye, any residual regular errors ofthe eye (such as differences between the selected tissue-shaping surfacepower and the measured refractive error of the eye), any asphericalpresbyopia-mitigating shapes, and/or the like, the total variation indepth of the target laser surface can be limited to a relatively narrowrange, even when correcting eyes having quite significant standardrefractive errors. As the irregular errors, residual errors, andpresbyopia-mitigating shapes may all be encompassed by surfaces that areclose to a plane (or other convenient surface) once the eye conforms tothe tissue-shaping surface, such an arrangement may allow intrastromallaser ablations to correct a wide range of patient refractive errorsdespite any limitations in the range of intrastromal focusing andablation depth variability.

Exemplary embodiments of the invention include sets of tissue-shapingbodies, with each body of the set corresponding to a standard refractiveerror or error range. Each body will typically have at least oneassociated tissue-shaping surface with an associated spherical power andan associated cylindrical power. By selecting an appropriate body havingspherical and/or cylindrical powers which substantially correspond tothose of the eye, and by conforming the tissue of the eye to the tissueshaping surface of that body, the capabilities of intrastromal laserablations for correction of a wide range of regular and irregularrefractive defects may be significantly enhanced.

Referring now to FIG. 1, an exemplary system 100 is suitable forcorrecting regular and irregular refractive errors of eye E. System 100generally directs laser energy from a femtosecond laser 102 to cornealtissues of eye E while those tissues are shaped by a selected shapingbody 104. Shaping body 104 is supported and positioned by anelectromechanical support structure 106, with the exemplary supportstructure having a series of motion stages for selectively positioningthe body relative to the tissues of eye E. Optics 108 of system 100selectively direct the laser energy from laser 102 into the cornealtissues, with the optics and support structure generally being under thecontrol of a system processor or computer 22.

Shaping body 104 is selected from among a set of alternative shapingbodies 110. As schematically illustrated in FIG. 1, the shaping bodiesof set 110 will often have a variety of differing spherical and/orcylindrical powers. The cylindrical and/or power differences (sometimesreferred to as power steps or increments) between shaping bodies of set110 may be related to the range of depths of a target laser surface thatwill be determined by processor 22 and implemented by laser 102 andoptics 108. For example, if system 100 has sufficient intrastromalablation depth variability to form target laser surfaces that providespherical adjustments to eye E of up to 1.0 D in spherical power, theset of shaping bodies 110 may (if no other adjustments were desired)have incremental power steps of 2 D of spherical power or less. Such aset of shaping bodies, might, for example, include shaping bodies having−2.0 D, 0 D, 2.0 D, 4 D . . . of spherical correction. A patient having2.2 D of spherical error could then be treated by using a 2 D sphericalshaping body, and by adding an additional 0.2 D of spherical correctionby appropriate shaping of the target laser surface used during thescanning of the laser energy. A patient with 1.7 D of spherical errormight be treated with the same 2.0 D shaping body, but with 0.3 D ofcorrection being removed via an appropriate target laser surfaceimplemented using optics 108 under the direction of processor 22.

It will often be advantageous to maintain some range in depth of thelaser scanning optics for correction of irregular stigmatism, impositionof presbyopia-mitigating shapes, and the like. As the range ofintrastromal ablation depth may be less than 3.0 D of correction withsome systems, the steps in power within set 110 will often be less than6.0 D. The range in power that can be effected by intrastromal ablationof a surface may be less than 1.0 D in many embodiments, so that thepower steps within set 110 will often be 2.0 D or less. Exemplarysystems may allow laser surface adjustments of 0.75 D or less, so thatthe steps between spherical and/or cylindrical powers of set 110 may be1.5 D or less, optionally being 1.0 D or less so as to providesufficient irregular error treatment, presbyopia mitigation, and thelike.

Shaping body 104 generally includes a distal tissue-shaping surface 112,with the tissue-shaping surface having a sphero-cylindrical shapecorresponding to the associated nominal refractive correction of thatbody. Where the target laser surface will, for example, be nominallyplanar (with adjustments from the plane for irregular errors, residualpowers, aspherical presbyopia-mitigation shapes, and/or the like), thetissue-shaping surface may directly have the curvature associated withits nominal power in corneal tissue. Where the target laser surface hasa nominal spherical shape, the tissue-shaping surface may differ fromthat nominal spherical shape per the body nominal power, and so on. Inthe exemplary embodiment, a cylindrical side surface extends from thedistal end of the body adjacent surface 112 to a flat (or optionallylens-shaped) proximal surface. The material along surface 112 (andtypically from surface 112 to the proximal surface) comprises a materialwhich is sufficiently transmissive of the laser energy from laser 102 toallow treatment eye E without overheating of the body, thetissue-shaping surface, and the engaged corneal tissues. Suitablematerials may comprise, for example, glass, a suitable polymer such asPMMA, or the like. Body 104 will generally include positioning surfaces114 that can be engaged by corresponding surfaces of the supportstructure 106 so as to accurately position the body horizontally (alongthe X-Y plane) relative to an optical axis 116 of the laser treatment(such as the cylindrical side surface, circular end walls and edges, orthe like), and also so as to rotationally position the body 104 aboutthe axis 116 (such as the notch illustrated). This will help facilitaterotational alignment of any cylindrical power of tissue-shaping surface112 relative to the cylindrical astigmatism axis of eye E. A widevariety of alternative shaping bodies might also be implemented.

Referring now to FIGS. 1 and 1A, elements of system 100 may beincorporated into, and/or may make use of components of a laser eyesurgery system 10. Laser eye surgery system 10 generally includes alaser system 12 and a patient support system 14. Laser system 12includes a housing that contains both a laser and a system processor 22.The laser generates the laser beam 18, which is directed to a patient'seye under the direction of a system operator. Delivery optics used todirect the laser beam, the microscope mounted to the delivery optics,and the like may employ existing structures from commercially availablelaser systems, including at least some portions of the excimerrefractive laser systems available from ADVANCED MEDICAL OPTICS, INC. ofSanta Clara, Calif.

In addition to (or in some cases, instead of) adjustment to the deliveryoptics directing laser beam 18, alignment between the patient and thelaser treatment system may be provided at least in part by the patientsupport system 14. Patient support system 14 generally includes apatient support 20 having an associated patient support movementmechanism. Patient support 20 may be contoured, helping to position thepatient at a nominal location on the patient support. Large and fineadjustments of the patient support and patient may be effected usinglarge and fine motion control mechanisms such as those more fullydescribed in U.S. patent application Ser. No. 10/226,867 filed on Aug.20, 2002, the disclosure of which is incorporated herein by reference.

FIG. 2 is a simplified block diagram of an exemplary computer system 22that may be used by the laser surgical system 100. Computer system 22typically includes at least one processor 52 which may communicate witha number of peripheral devices (and/or other processors) via a bussubsystem 54. These peripheral devices may include a storage subsystem56, typically including a memory 58 and a file storage subsystem 60. Theperipheral devices may also include one or more user interface inputdevice 62, user interface output device 64, and a network interfacesubsystem 66. Network interface subsystem 66 can provide an interface tooutside networks 68 and/or other devices, such as the wavefrontmeasurement system 30 described below with reference to FIG. 3.

User interface input devices 62 may include a keyboard, pointing devicessuch as a mouse, trackball, touch pad, or graphics tablet, a scanner,foot pedals, a joystick, a touch screen incorporated into the display,audio input devices such as voice recognition systems, microphones, andother types of input devices. User input devices 62 will often be usedto download a computer executable code from a tangible storage media 29embodying any of the methods described herein. User output devices 64may include a display subsystem, a printer, a fax machine, or non-visualdisplays such as audio output devices. The display subsystem maycomprise a cathode ray tube (CRT), a flat-panel display such as a liquidcrystal display (LCD), a projection device, or the like. The displaysubsystem may also provide a non-visual display such as via audio outputdevices. Storage subsystem 56 stores the basic programming and dataconstructs that provide the functionality of the various embodiments ofthe invention. For example, a database and modules implementing thefunctionality of the methods described herein may be stored in storagesubsystem 56. These software modules will generally be executed byprocessor 52. In a distributed processing environment, the softwaremodules may be stored on any of a plurality of computer systems andexecuted by processors of those computer subsystems. Storage subsystem56 typically comprises memory subsystem 58 and file storage subsystem60.

Memory subsystem 58 typically includes a number of memories including amain random access memory (RAM) 70 for storage of instructions and dataduring program execution, and a read only memory (ROM) 72 in which fixedinstructions are stored. File storage subsystem 60 may providepersistent (non-volatile) storage for program and data files, and mayinclude tangible storage media 29 (see FIG. 1) which may optionallyembody wavefront sensor data, wavefront gradients, a wavefront elevationmap, a treatment map, and/or an ablation table, as well as machinereadable code or programming instructions for implementing the dataprocessing and control methods described herein. File storage subsystem60 may include a hard disk drive, a floppy disk drive (along withassociated removable media), a compact digital read only memory (CD-ROM)drive, an optical drive, DVD, CD-R, CD-RW, solid-state removable memory,and/or other removable media cartridges or disks. One or more of thedrives may be located at remote locations or on other connectedcomputers at other sites coupled to computer system 22. The modulesimplementing the functionality of the present invention may be stored byfile storage subsystem 60.

Bus subsystem 54 provides a mechanism for letting the various componentsand subsystems of computer system 22 communicate with each other asintended. Although a single bus subsystem is shown schematically,alternate embodiments the bus may utilize multiple bus systems.

Computer system 22 can be of various types including a personalcomputer, a portable computer, a work station, a computer terminal, anetwork computer, a control system in a wavefront measurement system orlaser surgical system, a mainframe, or another appropriate dataprocessing system. As computers and networks change over time, thedescription of computer system 22 shown in FIG. 2 represents only anexample for purposes of illustration of an embodiment of the invention,and many other configurations of computer systems are possible.

As noted above, laser system 100 may correct both regular and irregularoptical errors of the eye. Regular optical errors (such as sphericalerrors associated with myopia and hyperopia, and cylindrical errorsassociated with standard cylindrical stigmatism) can be measured usingany of a wide variety of commercially available diagnostic devices,including phoropters, automated refractometers, trial lenses, and thelike. While a variety of devices and systems have also been developedand to measure irregular optical errors of the eye (includingtopographers, tomography systems, and the like) any irregularastigmatism or high-order aberrations of the eye will often be measuredusing a wavefront system.

Referring now to FIG. 3, one embodiment of a wavefront measurementsystem 30 is schematically illustrated in simplified form. In verygeneral terms, wavefront measurement system 30 is configured to senselocal slopes of a wavefront exiting the patient's eye. Devices based onthe Hartmann-Shack principle generally include a lenslet array to samplethe slopes across the pupil of the eye. Thereafter, the local slopes areanalyzed so as to reconstruct the wavefront surface or map, often usingZernike polynomial expansion methods.

More specifically, one wavefront measurement system 30 includes a lightsource 32, such as a laser, which projects a source image throughrefractive tissues 34 of eye E so as to form an image 44 upon a surfaceof retina R. The image from retina R is transmitted by the refractivesystem of the eye (e.g., refractive tissues 34) and imaged onto awavefront sensor 36 by system optics 37. The wavefront sensor 36communicates signals to a computer system 22′ for measurement of theoptical errors in the optical tissues 34 and/or determination of anoptical tissue ablation treatment program. Computer 22′ may include thesame or similar hardware as the computer system 22 illustrated in FIGS.1 and 2. Computer system 22′ may be in communication with computersystem 22 that directs the laser surgery system 10, or some or all ofthe computer system components of the wavefront measurement system 30and laser surgery system 10 may be combined or separate. If desired,data from wavefront sensor 36 may be transmitted to a laser computersystem 22 via tangible media 29, via an I/O port, via a networkingconnection 66 such as an intranet or the Internet, or the like.

Wavefront sensor 36 generally comprises a lenslet array 38 and an imagesensor 40. The reflected light from retina R is transmitted throughoptical tissues 34 and imaged onto a surface of image sensor 40 and theeye pupil P is similarly imaged onto a surface of lenslet array 38. Thelenslet array separates the transmitted light beam into an array ofbeamlets 42, and (in combination with other optical components of thesystem) images the separated beamlets on the surface of sensor 40.Sensor 40 typically comprises a charged couple device or “CCD,” andsenses the characteristics of these individual beamlets, which can beused to determine the characteristics of an associated region of opticaltissues 34. In particular, where image 44 comprises a point or smallspot of light, a location of the transmitted spot as imaged by a beamletcan directly indicate a local gradient of the associated region ofoptical tissue.

Eye E generally defines an anterior orientation ANT and a posteriororientation POS. Light source 32 generally sends light in a posteriororientation through optical tissues 34 onto retina R as indicated inFIG. 3. Optical tissues 34 again transmits light reflected from theretina anteriorly toward wavefront sensor 36. Image 44 actually formedon retina R may be distorted by any imperfections in the eye's opticalsystem when the image source is originally transmitted by opticaltissues 34. Optionally, image projection optics 46 may be configured oradapted to decrease any distortion of image 44.

In some embodiments, projection optics 46 may decrease lower orderoptical errors by compensating for spherical and/or cylindrical errorsof optical tissues 34. Higher order optical errors of the opticaltissues may also be compensated through the use of an adaptive opticssystem, such as a deformable mirror. Use of a light source 32 selectedto define a point or small spot at image 44 upon retina R may facilitatethe analysis of the data provided by wavefront sensor 36. Regardless ofthe particular light source structure, it will be generally bebeneficial to have a well-defined and accurately formed image 44 onretina R.

The wavefront data may be stored in computer readable medium 29 or amemory of the wavefront sensor system 30 in two separate arrayscontaining the x and y wavefront gradient values obtained from imagespot analysis of the Hartmann-Shack sensor images, plus the x and ypupil center offsets from the nominal center of the Hartmann-Shacklenslet array, as measured by the pupil camera 51 (FIG. 3) image. Suchinformation may include the available information on the wavefront errorof the eye and is typically sufficient to reconstruct the wavefront or adesired portion of it. In such embodiments, there may be no need toreprocess the Hartmann-Shack image more than once, and the data spacerequired to store the gradient array is not large. For example, toaccommodate an image of a pupil with an 8 mm diameter, an array of a20×20 size (i.e., 400 elements) is often sufficient. As can beappreciated, in other embodiments, the wavefront data may be stored in amemory of the wavefront sensor system in a single array or multiplearrays.

While embodiments of the invention will generally be described withreference to sensing of an image 44, it should be understood that aseries of wavefront sensor data readings may be taken. For example, atime series of wavefront data readings may help to provide a moreaccurate overall determination of the ocular tissue aberrations. As theocular tissues can vary in shape over a brief period of time, aplurality of temporally separated wavefront sensor measurements canavoid relying on a single snapshot of the optical characteristics as thebasis for a refractive correcting procedure. Still further alternativesare also available, including taking wavefront sensor data of the eyewith the eye in differing configurations, positions, and/ororientations. For example, a patient will often help maintain alignmentof the eye with wavefront measurement system 30 by focusing on afixation target, as described in U.S. Pat. No. 6,004,313, the fulldisclosure of which is incorporated herein by reference. By varying aposition of the fixation target as described in that reference, opticalcharacteristics of the eye may be determined while the eye accommodatesor adapts to image a field of view at a varying distance and/or angles.

Referring now to FIG. 4, treatment of eye E often begins by aligningbody 104 with the eye. Body 104 will often be moved horizontally (in theX-Y plain) so as to align an optical axis 116 of the laser treatmentsystem and tissue-shaping surface 112 with the corneal tissues. The eyemay be imaged through body 104 as schematically illustrated in FIG. 5,and known image processing techniques can be used to identify a positionand orientation of the eye with reference to a pupil P, features of theiris I, an outer edge of the iris or limbus L, or the like. Body 104and/or eye E may be moved horizontally so as to align a center C ofpupil P with a center 122 of surface 112. Additionally, body 104 may berotated about axis 116 so as to align an stigmatism axis A of eye E witha cylindrical axis 124 of surface 112.

Positioning of the eye E relative to body 104 may be determined using avariety of methods and systems for tracking torsional orientation andposition of an eye, including those described in U.S. patent applicationSer. No. 10/300,714, filed by the assignee of the present application onNov. 19, 2002, now published as U.S. Patent Publication No.US2003/0223037 A1), the full disclosure for which is incorporated hereinby reference. Such tracking techniques often make use of the striationsin the iris I and the location of the pupil boundary for torsional andhorizontal positioning, respectively. This information may be providedto the various motion stages of support system 106 (see FIG. 1) to drivebody 104 into alignment with the eye. Alternatively, the eye may bealigned with the axis 116 by relying, in at least some dimensions, uponfixation of the eye on a viewing target, with engagement between thetissue-shaping surface 112 into the eye occurring only when thealignment is within an acceptable range, such as when any alignmentoffsets are less than or equal to desired thresholds.

As will be described in more detail below, absolute alignment betweenpositioning surface 112 and the tissue of the eye need not be provided.So long as the alignment is within an acceptable range, some adjustmentof the effective location of the imposed refractive shape may beprovided by adjusting the laser target surface. If the engagementbetween the tissue-shaping surface 112 and eye is sufficientlyinaccurate that offsets (either horizontally, between pupil center C andsurface center 122, or torsionally between astigmatism axis A andcylinder axis 124) exceeds a desired threshold, then the body 104 may bedisengaged from the eye, the eye or the body repositioned, and the bodyagain being advanced into engagement with the eye. This may continueuntil the alignment offsets are within the desired thresholds. Thethresholds may be established so as to allow sufficient adjustment tothe final refractive correction using changes to the laser targetsurface, so that the depth range of the laser target surface may effectthe acceptable alignment offsets. Calculation of the laser targetsurface, and changes to the laser target surface so as to accommodatealignment offsets, may be implemented using any of a wide range ofoptical analytical tools that have been developed and commercialized,including those used for customized wavefront-based laser eye surgeryand the like.

Referring now to FIG. 6, once body 104 and the eye E are sufficientlyaligned, the body is pressed against the corneal tissues of the eye sothat the corneal tissues can form to the shape of surface 112. As can beunderstood with reference to FIGS. 6 and 7, the cornea need not conformto surface 112 throughout the entire tissue-shaping surface and/orcornea, so long as the cornea conforms to the desired shape throughoutan optically used portion U of the corneal tissues of eye E. While thecornea conforms to surface 112, the laser energy from the laser 102 (SeeFIG. 1) is focused at a spot 126, and the spot is scanned along a targetlaser surface 128 within the cornea.

Structures and methods for focusing and scanning the laser spot withinthe cornea so as to incise the corneal tissue are described in a varietyof references, including U.S. Pat. Nos. 6,325,792 and 6,899,707, thepatents and patent applications assigned to Intralase Corporation ofIrvine Calif., and the like. Laser systems and devices for formingincisions in the cornea using focused laser energy (often for use inLASIK procedures) may be commercially available from Intralase andothers. Known corneal laser incision techniques often incise the corneaalong a plane, often while the corneal surface is applanated so as toform a thin epithelial flap of relatively constant thickness.Embodiments of the present invention will often vary the target lasersurface from such a plane (or other standard surface shape, such as asphere or the like). Nonetheless, such embodiments will often limit arange of depth 130 of the target laser surface 128 as measured from aplane (or other surface). By conforming the corneal tissue to a standardrefractive shape such as by use of tissue-shaping surface 112, and byincising the cornea along a plane, a standard refractive correction ofthe cornea could be effected. By instead varying the depth of the targetsurface 128 from a nominal plane (or other shape) per any alignmentoffsets between the surface 112 and the eye, and per any desiredhigh-order alternations of the eye (such as those that may beimplemented for alleviation of presbyopia, the irregular refractiveerrors of the eye, or the like), a wide variety of refractiveimprovements may be made to the eye.

Referring now to FIG. 7A, the corneal tissues of the eye E generallyinclude an epithelial layer EP disposed over stroma S. After the laserhas incised the stroma and epithelial layer along target laser surface128, body 104 may be retracted proximally from engagement with the eye,so that the anterior tissue (including both epithelium and stroma)bordered by the laser target surface 128 may be mechanically removedfrom the eye. The tissue may be removed by grasping the tissue withmicro forceps, displacing the tissue using a flow of fluid (eitherliquid or gas), grasping the tissue using a vacuum applied through aport in surface 112 or a hand-held implement, or the like. Where thelaser target surface 128 has been determined based on the high-order forrefractive errors of the eye, and where the general curvature of theremaining incised tissue surface reflects the curvature oftissue-shaping surface 112, removal of this anterior tissue can effectboth high-order or irregular refractive correction and low-order orregular refractive correction of eye E. Appropriate tissue removalshapes may be determined using ray tracing or wavefront analysis,through empirical studies, and the like, and will often reflect theanticipated epithelial regrowth from the incision formed along thetarget laser surface. The incision need not be complete when body 104 isretracted, as small remaining contact points can optionally be separatedby pulling of the severed tissue body. Techniques developed tofacilitate formation of a LASIK flap, including the formation ofablation reservoirs, applanation lens support and vacuum tissueaffixation systems, alternating locations along the target surface toinhibit thermal damage, and the like, may be modified for use in laserincising of the corneal tissues along the target surface.

Referring now to FIGS. 8, 8A, and 8B, an alternative embodiment makesuse of two separated laser target surfaces and temporary deflection ofan epithelial flap so as to minimize delays for epithelial regrowth andthe like. As illustrated in FIG. 8, a first laser target surface 128 isdetermined based on the high-order aberrations of the eye and/or thelike. Laser spot 126 is scanned along first target surface 128, withincising of the tissue of the eye limited along one edge of the lasertarget surface. A second laser target surface 132 is determined, forexample, at a fixed distance from tissue-shaping surface 112, or from aflat planar surface similar to those used for formation of a standardLASIK flap. As illustrated in FIGS. 8A and B, again similar to standardLASIK, the flap may be temporarily displaced, allowing the cornealtissues between the first and second laser target surfaces 128, 132 tobe mechanically removed. The flap may then be laid back over themodified cornea, so that the tissues bordered by the laser targetsurfaces 128 and 132 engage and attach to each other. Once again, thefinal corneal surface will reflect both the regular refractivecorrection associated with tissue-shaping surface 112 and the high-orderaberration corrections of target laser surface 128, but without herehaving to wait for epithelial regrowth to enjoy the benefits of theprocedure.

As illustrated in FIG. 8C, alternative embodiments are also possible,such as by forming a planer posterior incision and a target laser 128reflecting the high order aberrations of the eye at an interiorposition. The tissue targeted for removal may extend to an exposedtissue region 134 engaged by body 104, and a vacuum port 136 of the bodymay be used to displace the flap and remove the tissue bordered by theincisions when body 104 is withdrawn proximally away from eye E.Additional ports in body 104 (or an adjacent structure of system 100)may provide fluid or gas flow to help separate the corneal tissues fromthe tissue-shaping surfaces and the like, to apply a vacuum to affix theengaged eye relative to the delivery optics, and the like. Asillustrated in FIG. 8D, alternative tissue-shaping bodies 104A mayinclude multiple tissue-shaping surfaces, such as a first tissue-shapingsurface 112 corresponding to a standard refractive error, and a planartissue-shaping surface 138 for formation of a uniform-thickness tissueflap during scanning along second laser target surface 132. Switchingbetween the tissue-shaping surfaces may be implemented using the motionstages of support structure 106. Still further alternatives areavailable, including applying any residual or high-order alterations onboth the posterior and anterior target laser surfaces, which mayincrease the total adjustment power available for a given intrastromaldepth adjustment range.

Referring now to FIG. 9, some of the optical and support systemcomponents are schematically illustrated. Shaping body 104 is mounted ina receptacle 140 having a rotational drive for rotating the shaping bodyabout the axis 116, as indicated by arrows 142. Translation of shapingbody 104 along axis 116 so as to engage the shaping body against eye Eis provided by a Z axis translation/engagement motion stage 144, whilehorizontal positioning of the shaping body in the X-Y plain is effectedusing a two dimensional X-Y translation stage 146. In some embodiments,one or more of these motions may be manually effected, such as by havingthe system user pre-position body 104 at an orientation appropriate forthe patient's astigmatism axis.

To effect lateral scanning of the laser energy from laser 102, a twodimensional scanning mirror 148 optionally pivots in two dimensions, asindicated by arrows 150. Alternative arrangements may employ a firstscanning mirror to scan the laser energy along the X axis, and a secondscanning mirror having a pivot axis angularly offset from that of thefirst mirror may provide scanning primarily along the Y axis. Stillfurther alternative scanning mechanisms may be employed, including X-Ytranslation of an offset imaging lens, and the like. Scanning of thelaser spot 126 along axis 116 may be effected by movement of one or morefocusing lens 152 along the optical path in between the laser and eye.As the scanning rate of the laser spot 126 within the tissue of the eyeE may be quite rapid, it will generally be beneficial to minimize theweight of any electro mechanical scanning elements, drive the scanningelements with relatively high speed actuators such as galvanometers, andthe like.

Many of the remaining optical and control components of system 100 maybe similar to (or modified from) components of existing laser eyesurgery systems. For example, the optical path may employ a series ofbeam splitters 154 to selectively direct portions of the light from eyeE, optionally using wavelength-selective reflection. An image sensor 156may capture an image of the eye through shaping body 104 and othercomponents along the optical path, with the captured image often beingused for establishing and/or verifying alignment between the eye andshaping body 104, laser spot 126, and other components of the opticalpath. Signals from the image sensor 156 may be used to identify a centerof the pupil of eye E, a rotational orientation of eye E, and the like.Such signals may be used to drive the various motion stages of supportstructure 106 and movable optical components of optics 108 percalculations of processor 22 (See FIG. 1). Images from image sensor 156may also be used to measure alignments offsets and the like as describedabove. Images may also be displayed on a display screen of the laser eyesurgery system, which may be used in conjunction with (or instead of)direct viewing of the procedure through binocular microscope 158.Additional optical and/or mechanical components of system 100 may alsobe included, including a fixation target 160, additional lenses andgroups of lenses for processing the light on the optical path, and thelike.

Referring now to FIGS. 10A and 10B, top and side views, respectively, ofa support arm 162 show many of the components described above regardingsupport system 106. The rotational stage of receptacle 140, the axialtranslation stage 144, and the horizontal motion stage 146 may bearranged in a variety of differing orders, or may be combined orseparated into fewer or more individual stages having different degreesof freedom in a wide variety of possible arrangements. The receptacle140 will preferably receive shaping body 104 and engage positioningsurfaces of the shaping body so as to allow accurate positioning androtation of the shape and body into alignment with the eye. While asimple latch of the receptacle is schematically illustrated, nostructure of the receptacle will typically extend beyond the shapingbody so as to interfere with engagement between the shaping surface 112and the eye E.

Referring now to FIG. 11, a method 200 may be used to correct regularrefractive errors of the eye and impose desired irregular refractivealterations, such as correcting high order aberrations of the eye,impose multifocal shapes on the eye suitable for mitigating presbyopia,and the like. Method 200 will often begin with measurement of theoptical characteristics of the eye 202, with exemplary measurementscomprising wavefront measurements and/or otherwise providing informationon both regular and irregular refractive errors of the eye. A shapingbody will be selected 204 having a tissue-shaping surface thatsubstantially corresponds to a regular error of the eye.

Substantially corresponding shapes may have shapes which correspondexactly to the refractive error of the eye, or which are the closestcorresponding spherical and/or cylindrical powers available within agiven set of alternatively selectable tissue-shaping surfaces. In manyembodiments, particularly those in which additional high-orderadjustments to the eye prescription will be made, the substantiallycorresponding body may not be the single closest corresponding shape,but will often be among the subset of shaping bodies having powers whichare the nearest more positive spherical and/or cylindrical power, thenearest more negative spherical and/or cylindrical power, or the like.Hence, where a set of shaping bodies has uniform one diopter incrementsin both cylindrical and spherical power, an eye having 2.2 diopters ofthe sphere and 3.3 diopters of cylinder may be treated by selecting ashaping body having spherical, cylindrical powers of: (2, 3), (3, 3),(2,4), or (3, 4). In some embodiments, particularly when high levels ofirregular refractive alterations will be imposed and/or when the set ofalternatively selectable shaping bodies has small increments in power,the set may include a shaping body which has a power that is betweenthat of the regular refractive error of the eye and that of the selectedsubstantially corresponding shaping body. Such circumstances may be theexception, and the substantially corresponding shaping body willtypically be closer to the measured standard refractive error of the eyethan most of the non-selected shaping bodies of the set, and oftencloser than at least 75% of the shaping bodies of the set.

Based on the measured optical characteristics of the eye 202 and theselected shaping body 204, a custom laser target surface shape orprescription 206 will be determined. As described above, the customprescription may be determined from the irregular refractive shape,and/or from any residual regular error that would otherwise remain ifthe tissue-shaping surface power alone or used. Hence, in our example ofan eye having 2.2 D of spherical error and 3.3 D of cylindrical error,assuming a 2 D sphere/3 D cylinder body is selected, the target lasersurface will be adjusted so as to provide an additional 0.2 D of sphereand 0.3 D of cylinder. Any additional refractive changes, such asmultifocal shapes to mitigate presbyopia (such as those more fullydescribed in U.S. patent application Ser. No. 10/738,358, filed on Dec.5, 2003, and entitled “Presbyopia Correction Using Patient Data”, thefull disclosure of which is incorporated herein by reference) may alsobe included. The target laser surface can then be compared with anydepth range or threshold 208. If the target laser surface has variationsin depth which exceed the capabilities of the laser system or a saferange for the cornea of that particular patient, an alternative shapingbody may be selected, and/or some modification of the proposed customlaser target surface may be calculated so as to provide a viableprescription.

Once the shaping body and custom prescription are identified, theshaping body is mounted to the laser system 210. The system may verifythat the shaping body is appropriate for the patient 212, often by atransmission of signals between the processor 22 of system 100 and asignal source 98 of shaping body 104 (See FIG. 1). The signal source 98may comprise a memory chip, a radio frequency identification (RFID)structure or tag of body 104, or the like. The signals transmitted fromthe signal source 98 may comprise or indicate the power of thetissue-shaping surface 112 of the mounted body 104, and may alsoidentify that particular mounted body. The processor can use thesesignals to verify that the mounted body has the appropriate power forthe corrected custom prescription of the eye, and may also verify thatthe particular body mounted on the system has not already been used in aprior procedure so as to present dangers to the patient due todegradation in the optical qualities of the shaping body, sterilizationissues, and the like. The transmitted signals may also be used to verifythat the shaping body is suitable for use on the laser system on whichit is mounted (avoiding incompatibility issues), to verify regulatoryapproval of the combination of the mounting body and system for use intreating the patient, to verify that the system user (as entered intothe system via an input device) has appropriate training for theprocedure, and/or to allow the manufacturer and/or a regulatory body tomonitor use of that particular laser treatment system. By controllingdistribution of bodies 104 having appropriate signal sources, themanufacture may also collected fees from the user of the system 100,with monitoring and/or fee collection often being performed via anetwork coupled to processor 22. If processor 22 determines the shapingbody is not appropriate for use in the procedure for any reason, theprocessor may, in response, inhibit or prevent the procedure from goingforward and the eye from being treated with that shaping body.

Once the shaping body has been verified, the shaping body will berotated so as to align the cylindrical axis (if any) of tissue-shapingsurface 112 on the cylindrical body with an astigmatism access of theeye. The patient will be positioned for treatment 216, and the shapingbody preregistered with the eye 216 (often using an image of the eyetaken through the shaping body as described above). The order of theaxial rotation of the shaping body, positioning of the patient, andpreregistration of the shaping body with the eye 218 may be altered asappropriate, and at least some of these alignment steps may beimplemented manually. For example, the patient and/or chair may bemanually positioned by the physician, the eye may be aligned at least inpart by having the patient view a fixation target, and/or the shapingbody (optionally with its receptacle) may be manually rotated intoalignment with patient's astigmatism axis.

When the shaping body and the eye appear to be the appropriatelypreregistered, the tissue-shaping surface and the shaping body areadvanced into engagement with the eye 220 so as to conform the tissuesof the cornea with the shape of the tissue-shaping surface. Horizontaland/or rotational engagement offsets are measured, typically by imagingthe eye through body 104 and using image processing techniques such asthose that have been developed for tracking of the eye during knownlaser eye surgery procedures. Measured offsets 222 may be used to modifythe custom prescription, for example, so as to compensate for rotationaloffsets between the cylindrical power axis of the shaping body and theastigmatism axis of the eye, so as to laterally offset the cylindricalpower and/or spherical power, or the like. Known optical shapecalculation methods may be employed for such modification of the customprescription 224, and the custom prescription may again be checkedagainst depth thresholds 226 of the laser system and/or patient cornea.If the engagement offsets are excessive and/or the custom prescriptiondepths now exceeds the allowable range, the shaping body may bedisengaged 228, with re-registration and re-engagement hopefullyproviding an acceptable custom shape.

As described above regarding claims 7 and 7A, laser incising on thecustom prescription 230 may be used to sever a desire to shape from theanterior corneal surface, so that epithelial regrowth provides thedesired enhanced refractive characteristics. Alternatively, as describedwith reference to FIGS. 8A through C, a second laser incision 232 may beimplemented, with tissue removed from between the two incisions so as toretain the existing epithelial layer of the cornea. It should be notedthat the incisions need not absolutely sever the tissues from the eye,as any relatively small remaining connection points may be detached bymechanical excision, such as by simply pulling the substantially severedtissues.

After ablation along the target laser the surface or surfaces iscomplete, shaping body 104 may be retracted 234 away from the eye E andthe desired tissue excised from along the one or more target lasersurfaces 236.

While the exemplary embodiments have been described in some detail, byway of example and for clarity of understanding, a variety ofmodifications, changes, and adaptations will be obvious to those ofskill in the art. Hence, the scope of the present invention is limitedsolely by the appended claims.

1. A method for altering refraction of an eye, the eye having a regularrefractive error and capable of benefiting from desired irregularrefractive alteration, the method comprising: selecting a tissue-shapingsurface from among a set of alternative shaping bodies havingtissue-shaping surfaces corresponding to differing regular refractiveerrors, the selected tissue-shaping surface substantially correspondingto the regular refractive error; engaging the selected tissue-shapingsurface against the eye so as to conform the eye to the selectedtissue-shaping surface; determining a three-dimensional laser targetsurface in response to the desired irregular refractive alteration ofthe eye; and scanning a laser spot in three-dimensions through tissue ofthe engaged eye along the laser target surface so as to mitigate theregular error and effect the desired irregular refractive alteration ofthe eye.
 2. The method of claim 1, wherein the set of alternativeshaping bodies define a series of spherical and cylindrical steps inpower therebetween, wherein the selected tissue-shaping surfacecorresponds with a selected power, the selected power differing from theregular error of the eye by a power difference, the power differencebeing less than an associated step in power of the shaping bodies, andwherein the laser target surface is also determined so as to compensatefor the power difference.
 3. The method of claim 2, wherein the steps inpower are each less than or equal to two times a maximum poweradjustment of the laser target surface.
 4. The method of claim 2,wherein the steps in power are less than or equal to 3.0 diopters. 5.The method of claim 2, further comprising adjusting the laser targetsurface per a desired presbyopia-mitigation shape.
 6. The method ofclaim 1, wherein each of the set of alternative selectabletissue-shaping surfaces is disposed on a shaping body comprises a lasertransmissive material having laser delivery alignment surfaces and asignal source, the signal source configured to generate signalsindicative of an associated power and an identifier of that particularbody, and further comprising verifying mounting of an appropriate bodyfor the eye and inhibiting re-use of each of the alternative selectablebodies using the signals.
 7. The method of claim 1, wherein the regularerror of the eye comprises a cylindrical error having an astigmatismaxis, and further comprising rotating the tissue-shaping surface intoalignment with an astigmatism axis of the eye.
 8. The method of claim 1,further comprising checking alignment between the tissue-shaping surfaceand the eye after engaging the tissue-shaping surface against the eye.9. The method of claim 8, wherein the alignment is checked by capturingan image of the engaged eye and determining a horizontal offset andcyclotorsional offset between the engaged eye and the tissue-shapingsurface, and further comprising, in response to one or both of theoffsets exceeding an alignment threshold, displacing thetissue-reshaping surface away from the eye, moving the eye or thetissue-shaping surface to correct alignment, and re-engaging thetissue-shaping surface against the eye.
 10. The method of claim 8,further comprising adjusting a location of the target laser surfacerelative to the tissue-shaping surface and a shape of the target lasersurface in response to an alignment offset between the tissue shapingsurface and the eye.
 11. The method of claim 1, further comprisingmechanically excising tissue from between the target laser surface andthe tissue-shaping surface so that the eye has enhanced refractivecharacteristics after re-growth of removed epithelial tissue.
 12. Themethod of claim 1, further comprising scanning the laser spot alonganother laser target surface so that first and second tissue surfacesare defined by the laser target surfaces, and mechanically excisingtissue from between the first and second tissue surfaces so that the eyehas enhanced refractive characteristics when the first tissue surfaceengages the second tissue surface.
 13. The method of claim 1, whereinthe laser spot comprises a femtosecond laser spot and separates thetissue of the eye along the laser target surface in about 30 seconds orless, and wherein separated tissue bordered by the laser target surfaceis primarily mechanically removed rather than primarily relying onvolumetric photoablative resculpting.
 14. A method for customizedcorrection of an eye, the method comprising: measuring a regularrefractive error and an irregular refractive error of the eye, theregular refractive error comprising a spherical error and a cylindricalerror, the cylindrical error having a cylindrical power and anastigmatism axis; selecting a tissue-shaping body in response to theregular refractive error of the eye from among a set of alternativetissue-shaping bodies having differing associated spherical andcylindrical powers, the selected tissue-shaping body having a selectedtissue-shaping surface, a spherical power substantially corresponding tothe spherical error of the eye, and a cylindrical power substantiallycorresponding to the cylindrical error of the eye; aligning acylindrical axis of the selected tissue-shaping body with theastigmatism axis of the eye; engaging the, selected tissue-shapingsurface against the eye so as to conform an eye surface to the selectedtissue-shaping surface; determining a three-dimensional target lasersurface in response to the irregular refractive error of the eye;incising tissue of the eye by scanning a laser spot in three dimensionsthrough the tissue along the laser target surface; and mechanicallyexcising tissue bordered by the laser target surface so as mitigate theregular refractive error and the irregular refractive error of the eye.15. The method of claim 14, wherein the target laser surface differsfrom a nominal surface shape by less than a depth threshold, the depththreshold corresponding to a power of about 1.5 diopters or less.
 16. Asystem for altering refraction of an eye, the eye having a regularrefractive error and is capable of benefiting from a desired irregularrefractive alteration, the system comprising: a set of alternativetissue-shaping bodies having tissue-shaping surfaces and differingregular refractive powers; a tissue incising laser for transmitting alaser beam along an optical path; a support for positioning a selectedtissue-shaping body along the optical path, the selected tissue-shapingbody selected from among the set; a processor for determining athree-dimensional laser target surface in response to the desiredirregular refractive alteration of the eye; and beam scanning opticscoupled to the processor for scanning the beam in three dimensions alongthe laser target surface to incise tissue from the eye when the eyeengages and conforms to the selected tissue-shaping surface such thatremoval of the incised tissue mitigates the regular errors of the eyeand effects the desired irregular alteration.
 17. The system of claim16, wherein the set of alternative shaping bodies define a series ofspherical and cylindrical steps in power therebetween.
 18. The system ofclaim 17, wherein the steps in power are each less than or equal to twotimes a maximum power adjustment of the laser target surface.
 19. Thesystem of claim 17, wherein the steps in power are less than or equal to3.0 diopters.
 20. The system of claim 17, wherein the selectedtissue-shaping surface corresponds with a selected power, the selectedpower differing from the regular error of the eye by a power difference,the power difference being less than an associated step in power of theshaping bodies, and wherein the processor is configured to determine thetarget laser surface so as to compensate for the power difference. 21.The system of claim 16, wherein the processor is configured to adjustthe laser target surface per a desired presbyopia-mitigation shape. 22.The system of claim 16, wherein each of the set of alternativeselectable tissue-shaping surfaces is disposed on an associated shapingbody, the shaping bodies comprising a material transmissive to the laserbeam and having laser delivery alignment surfaces and a signal source,the signal source configured to generate signals indicative of theselected power and an identifier of that particular body, the signalssuitable for inhibiting re-use of the alternative selectable bodies. 23.The system of claim 16, wherein the regular error of the eye comprises acylindrical error having an astigmatism axis, and wherein the supportrotatably supports the tissue-shaping surface about the optical path foralignment of the tissue-shaping surface with the astigmatism axis of theeye.
 24. The system of claim 16, further comprising an image capturedevice optically coupled to the optical path for imaging the eye whenthe eye engages the tissue-shaping surface, the processor coupled to theimage capture device and configured to determine alignment between thetissue-shaping surface and the eye after engaging the tissue-shapingsurface against the eye.
 25. The system of claim 24, wherein theprocessor is configured to determine a horizontal offset andcyclotorsional offset between the engaged eye and the tissue-shapingsurface in response to alignment data from the image capture device, andwherein the support further comprises a displacement stage coupled tothe processor for displacing the tissue-reshaping surface away from theeye and re-engaging the tissue engagement surface against the eye inresponse to one or both of the offsets exceeding an alignment threshold.26. The system of claim 25, wherein the processor is further configuredfor adjusting a location of the target laser surface relative to thetissue-shaping surface and a shape of the target laser surface inresponse to an alignment offset between the tissue shaping surface andthe eye.
 27. The system of claim 16, wherein the processor is configuredto scan the laser spot along another laser target surface so that firstand second tissue surfaces are defined by the laser target surfaces, andsuch that mechanically excising tissue from between the first and secondtissue surfaces and engaging the first tissue surface with the secondtissue surface enhances refractive characteristics of the eye.
 28. Thesystem of claim 16, wherein the laser comprises a femtosecond laser andthe processor is configured to separates the tissue of the eye along thelaser target surface in about 30 seconds or less.
 29. A tissue-shapingbody for use with a system for altering refraction of an eye, the eyehaving a regular refractive error and an irregular refractive error, thesystem including a support for positioning the body along an opticalpath from a laser, and beam scanning optics for scanning inthree-dimensions along a three-dimensional laser target surface toincise tissue of the eye when the eye engages the body such that removalalong the incised tissue mitigates the regular and irregular errors ofthe eye, the body comprising: a material transmissive of light from thelaser; and a tissue-shaping surface defined by the material, thetissue-shaping surface having a cylindrical power substantiallycorresponding to the regular refractive error of the eye.
 30. The bodyof claim 29, further comprising a signal source for transmitting asignal, the signal indicative of the cylindrical power and an identifierof the particular body suitable for inhibiting re-use of the body. 31.The body of claim 30, further comprising a set of alternativelyselectable tissue-shaping bodies having differing tissue-shapingsurfaces corresponding to differing cylindrical and spherical refractivepowers.